The use of illumination sources is widespread. In the medical industry illumination uses range from large overhead light sources for the operating arena to small sources delivered endoscopically through fiber optic bundles. Bulb based light sources encounter difficulties when focused into small fiber bundle because this type of light source illuminates in all directions. Historically, complicated optical focusing schemes using mirrors, lenses or a series or lenses and mirrors have been utilized to focus omni-directional light sources into fiber bundles. These schemes for illumination are problematic in that these schemes are usually not very efficient and much of the light is lost as heat. In addition, fiber optic bundles which are utilized in these systems are not very durable and can be very difficult to assemble without breaking. Fiber bundles also present a size constraint as well.
With the advent of solid state light sources (e.g. light emitting diodes (LED), white LED) much development has taken place to convert the monochromatic light output of an LED into broad spectrum white light. These sources are very efficient and compact, but as with bulb based light sources, they are very difficult to efficiently focus into a small fiber optic. The size of the light source is therefore limited to the emitter size of a diode or a number of diodes stacked together.
The laser was invented nearly 50 years ago and in the intervening time many different wavelengths of highly directed and focused light have been generated. Furthermore, laser technology has become more cost effective with the production of laser diodes and solid state laser technology.
Light sources have been used for many years during ophthalmic procedures. Particularly in vitreo-retinal surgery stand alone light sources attached to needles have been used to locate the anatomy of interest and to illuminate the general area of interest during a procedure. Current light sources often employ a light bulb powered by an electrical power supply. These light bulbs can be xenon, halogen or metal halide bulbs. There are many limitations of the currently marketed light sources such as the fact that the light emitting from the bulb spreads out in all directions making it difficult to focus the light into small fiber optics for insertion into the eye. Corrections for this problem often entail surrounding the bulb by a parabolic mirror and attempting to focus the light into a high numerical aperture fiber bundle. Unfortunately, the size of the light emitted from the bulb limits the amount of light to be focused into the smaller fiber bundle. The coupling between the light source and the fiber is generally very inefficient and results in light being converted into heat on the fiber connector. Another limiting factor in this design is the output of the light from the fiber. The numerical aperture (NA) of the fiber limits the output of the light to a cone corresponding to the fiber NA. Thus, a physician using this type of device would only be able to see the area illuminated by the NA of the fiber and nothing wider. Bulb based sources also emit light from the ultraviolet (UV) to the infrared (IR). Much of the light is harmful and wasted because they are invisible to the eye. Light sources that emit at these wavelengths require filtering to protect the eye from these harmful wavelengths.
Bulb based light sources and fiber bundles also have reliability limitations. The light bulbs burn out after a few hundred hours or less. In addition, fiber bundles are very brittle. If the fiber bundles break the total light output is significantly reduced. Additionally, the design is limited by the size of the fiber bundle such that if the fiber bundle is made smaller the total amount of light emitting from it decreases.
US Patent Application No. 2008/0051632 describes an illumination device comprising a laser light source with a fluorescent substance for illumination and visualization for endoscopic examination.
U.S. Pat. No. 5,651,783 describes a fiber optic integrated phacoemulsification system which incorporates fiber optic bundles that transmit visible light to enhance visualization by intraocular illumination.
U.S. Pat. No. 6,015,403 describes a probe for ophthalmic surgery utilizing a laser light source or an illumination source and an optical fiber for transmitting light from the light source to the eye to be treated.
There is a need for the efficient delivery of broad spectrum light for illumination in small compact confined spaces, like those required for ophthalmic surgery. The present invention provides solutions to many of the problems that exist in the currently marketed illumination devices. The illumination devices of the present invention are laser based so focusing the beam into a single small fiber can be more easily accomplished. Coupling efficiencies of 96% or greater can be achieved, which limits the problem of excess heating at the coupler. The use of lasers as a light source also greatly increases the electrical efficiency because all of the light is used for the output and little or no energy is wasted. Single fibers may be coated and structurally supported so mechanically the fibers are much stronger than fiber bundles that can be very brittle. Laser lifetimes are generally around 10,000 hours rather than the few hundred hours of life for a bulb based system. The laser light used in the present invention is safer to the eye than UV wavelengths. The white light spectrum is controlled by one or more light conversion medium so no filtering may be required. Inherently there are less harmful wavelengths emitted to the treatment area. Finally, because the light source effectively is at the output of the device, the light output can be controlled to be as wide as possible providing the largest possible field of view for the physician.